public class Test {
    public static void main(String[] args) {
        MySingleList head=new MySingleList();
        head.addFirst(1);
        head.addFirst(2);
        head.addFirst(3);
        head.addLast(4);
        head.addLast(5);
        head.addLast(6);
        head.addIndex(1,9);
        head.contains(2);
        head.removeAllKey(1);
        System.out.println(head.size());
        head.display();
    }

}
